Contribution of y-amino butyric acid to the mechanism of the negative feedback of the hypothalamo-hypophyseo-gonadal complex

Abstract

The role of y-aminobutyric acid (GABA) and its receptors in the regulation of negative feedback mechanisms of the integral hypothalamo-hypophyseo-gonadal complex was studied in sham-operated and unilaterally castrated Wistar rats. An increase of GABA content in the body by aminoacetic acid, an inhibitor of GABA-transaminase, was associated with a suppression of the compensatory rise of testosterone level in the peripheral blood after its two- or threefold drop caused by castration, whereas a reduction of GABA content with thiosemicarbaside, an inhibitor of glutamate decarboxylase, was paralleled by a more intensive compensatory increase of testosterone level. All GABA receptors participate in its action. Stimulation of GABA receptors with muscimol suppressed, and their blocking with bicucullin intensified the compensatory increase of testosterone level following hemicastration. At the same time, stimulation of GABA B receptors with baclophene was paralleled by a more intensive compensatory rise of blood testosterone level. The authors come to a conclusion that GABAergic systems contribute to regulation of the function of the hypothalamo-hypophyseo-gonadal complex as a negative feedback mechanism.